Performance. Zend Optimizer+ has a consistent performance edge over APC, which, depending on the code, can range between 5 and 20% in terms of requests/second. See Benchmarks section below.

Availability for new PHP versions. Optimizer+ is typically fully compatible with PHP releases even before they come out; While this advantage was rarely realized because of the closed-source nature of the component, once open-source, both Zend and the community will help ensure that it’s always fully compatible with every element of the PHP language, avoiding any lags.

Reliability. Optimizer+ has optional corruption detection capabilities that can prevent a server-wide crash in case of data corruption (e.g. from a faulty implementation of a PHP function in C). This handles one of the very few downsides of using a shared-memory-based-opcode-cache - introducing a shared resource that - if corrupted - could bring down an entire server.

Better compatibility. We strived to make Optimizer+ work with any and all constructs supported by PHP, in exactly the same way they’d behave without it.

Advantages of APC over Optimizer+

Has a data caching API. APC has a data caching API which Optimizer+ does not have.

APC can reclaim memory of old invalidated scripts. APC uses a memory manager and can reclaim memory associated with a script that is no longer in use; Optimizer+ works differently, and marks such memory as ‘dirty’, but never actually reclaims it. Once the dirty percentage climbs above a configurable threshold - Optimizer+ restarts itself. Note that this behavior has both stability advantages and disadvantages.

We expect beta 2 around April 4th, but that could get pushed back some (as beta 1 was also pushed back). While dates are something the Php Development Team likes to strive for.... The general idea is to have it stable and secure as possible (as always). So overall its ready when its ready.

We expect beta 2 around April 4th, but that could get pushed back some (as beta 1 was also pushed back). While dates are something the Php Development Team likes to strive for.... The general idea is to have it stable and secure as possible (as always). So overall its ready when its ready.